Mini-fans serve, for example, to cool processors in computers, for the cooling of small equipment items, etc. and have very small dimensions.
For example:
                fans of the ebm-papst 250 series have dimensions of 8×25×25 mm;        those of the ebm-papst 400F series, dimensions of 10×40×40 mm;        those of the ebm-papst 400 series, 20×40×40 mm; and        those of the ebm-papst 600 series, 25×60×60 mm.        
The power consumption of such fans is 0.4-0.6 W for the 250 series, 0.7-0.9 W for the 400F series, and 0.9-3.4 W for the 400 and 600 series. The weight is, for example, approximately 5 (five) grams for the 250 series, between 17 and 27 g for the 400/400F series, and approximately 85 g for the 600 series.
With fans of this miniature size, which must be very inexpensive, it is important to make assembly as simple as possible in order to enable a high level of automation during manufacture. Only extensive production automation additionally makes possible uniform quality in such fans, which is a prerequisite for a long average service life.
A complicating factor with such mini-fans is furthermore that their components, entirely comparable to those of a mechanical watch mechanism, are very delicate and therefore not robust. The rotor shaft, for example, is often only as thick as a knitting needle, and can therefore easily be bent if handled carelessly, rendering the fan unusable. This danger exists in particular during the assembly of such a mini-fan, for example when it must be acted upon by a force for assembly purposes.